A man has been arrested by police investigating an arson attack at a flat in which two apprentice jockeys died and two others were injured.

North Yorkshire Police said the man was being quizzed by detectives investigating the fatal blaze at the three-storey block in Norton, near Malton. The two people that died are yet to be named but police said two others were being treated in hospital in York for their injuries.

Eyewitnesses said survivors jumped out of windows to flee the blaze at the three-storey block near Malton, North Yorkshire. Emergency services were called to Buckrose Court, in Norton, at around 2.15am.

A North Yorkshire Police spokeswoman confirmed two people had died but officers were waiting for next of kin to be informed before formally identifying them. "Two other casualties, two men believed to be in their early 20s, have been taken to York District Hospital where they are being treated for the effects of smoke inhalation and burn injuries," she said. "It is too early to say what the cause of the fire was but a detailed examination of the scene will be carried out."

This morning, police had cordoned off a stretch of the high street and a number of fire appliances were still at the scene, at the end of the alleyway. The only signs of the blaze visible from the pavement were two charred window frames, on the first floor of the red-brick property overlooking a churchyard.

Trainer John Quinn, who runs stables at Malton, North Yorkshire, was on his way to the scene of the fire to speak to investigating officers. "There is no confirmation who has died," he said. "It's awful. I am just hoping we'll know something soon. I am not even sure if the people assumed to be dead are still in the building. It's just a nightmare."

Jockeys in action at Haydock and Stratford this afternoon are wearing black armbands and a 30-second silence was held before racing. Kempton and Thirsk also staged a period of silence in remembrance. York racecourse, which is staging a fixture tomorrow, is flying its flags at half-mast.

Catherine Hyder, who lives opposite the flats, said: "My husband heard a girl come down onto the street and [she] was banging on doors to raise the alarm. She said someone had jumped out of one of the windows. We could see the flames at the back and there were a lot of fire brigade people around. It was quite scary and quite noisy."

Another witness, Steve Kinsella, the landlord of the Railway Tavern, described how he was first made aware of the incident when a girl came into the street screaming.

"I just heard someone shouting," he said. "So I looked through the window and saw a girl just running in the street. All she had on was a t-shirt. She was shouting, 'Fire! Fire!', screaming at the top of her voice. I was just about to pick up the phone to dial 999 myself but as I had the phone in my hand the fire brigade turned up."

Mr Kinsella said police asked him to open up his pub and up to 20 people evacuated from the flats came inside to recover. He said at that point he did not realise anyone had died, although he knew the incident was serious. Asked how the residents were in his pub, he said: "They were shocked but quiet. Nobody was hysterical. They were very, very dignified."